The outcome of multiple pregnancy.

The incidence of multiple pregnancy and delivery has increased dramatically over the past 10-15 years in many developed countries of the world. Data for England and Wales show that between 1980 and 1993 the twin maternity rate increased by approximately 25% and the triplet and higher order maternity rate more than doubled. Similar trends have been reported elsewhere. The majority of these increases have been linked to the use of ovarian stimulants and assisted reproduction techniques, and multiple pregnancy must be considered to be one of the most important adverse outcomes in current methods of infertility treatment. Obstetric complications associated with multiple pregnancy include prenatal screening problems and increased incidence of pregnancy-induced hypertension, antepartum haemorrhage, preterm labour and assisted or surgical delivery. Neonatal problems include low birthweight and increased prevalence of congenital malformations. Compared with singletons, neonatal mortality was seven times higher in twins and > 20 times higher in triplets and higher order births in England and Wales in 1991. Survivors also suffer higher rates of cerebral palsy and other neurological impairments. Most studies of pregnancies and babies resulting from assisted reproduction have demonstrated similar, if not higher, risks of adverse obstetric and neonatal outcomes for multiple births compared with national expectations. A poorer outcome in multiple pregnancy, especially in triplet and higher order pregnancy, supports the replacement of two good quality embryos in assisted reproduction treatment cycles.